The present invention is concerned with susceptors of the type employed to support a plurality of disc-like substrates or the like, typically silicon discs or wafers, within a reactor during a high temperature vapor deposition operation. This particular process is well-known in the art, see, for example, Rosler U.S. Pat. No. 3,796,182, and the McNeilly et al U.S. Pat. No. 3,623,712 cited therein as disclosing a cool wall radiation heated system.
To assist in achieving uniform deposition, it is conventional practice to rotate the susceptor during the deposition process and the susceptor is therefore constructed to be symmetrical about a vertical axis of rotation. Because the discs which the susceptor is to hold are flat, the conventional susceptor configuration is of a polygonal transverse or horizontal cross section with the respective sides inclined inwardly toward the axis in their upward extent. Each of the polygonal side surfaces is conventionally formed with a plurality of circular pockets in which the discs are placed. The susceptors are conventionally formed of graphite coated with a silicon carbide coating or another material which is opaque to radiant heat energy and absorbs the same to be heated thereby, for reasons well-known to those skilled in the art.
Today's typical susceptor is conventionally constructed as a one-piece or permanently assembled article. As noted in the above identified Rosler patent, it is much more convenient to load the discs to be treated onto the susceptor when the face upon which the discs are being loaded is in a horizontal position. Because the discs merely rest in their pockets, it is not possible with a one-piece or permanently assembled susceptor to dispose all of the side surfaces in a horizontal position during the loading operation. The solution to this problem proposed in the Rosler U.S. Pat. No. 3,796,182 is to construct each of the side surfaces of the susceptor in the form of a separate slab which can be loaded in a horizontal position and then hung onto a frame.
While the Rosler patent broadly teaches the advantages of constructing a susceptor with removable side walls, the structural arrangement proposed by Rosler has several disadvantages. As pointed out by Rosler, in addition to functioning as a holder for the discs, the susceptor itself absorbs heat from the reactor and transmits this heat to the discs which it holds during the deposition process. In monitoring this process, heat sensors are located to sense the temperature of the susceptor slabs and modulate the heat radiation producing lamps accordingly. In order to obtain an accurate or undistorted reading from the heat sensors, it is necessary to shield the sensors from direct exposure to the susceptor surrounding radiant heating elements of the reactor. The individual slabs of the Rosler arrangement are widely spaced from each other which makes such shielding difficult.